The subject matter disclosed herein relates to a system and method for detecting spall within a turbine engine.
Certain gas turbine engines include a turbine having viewing ports configured to facilitate monitoring of various components within the turbine. For example, a pyrometry system may receive radiation signals through the viewing ports to measure the temperature of certain components within a hot gas path of the turbine. The pyrometry system may include an optical sensor configured to measure the intensity of radiation emitted by the turbine components within a fixed wavelength range. As will be appreciated, by assuming an emissivity, the temperature of the components may be determined based on the radiation intensity at a particular wavelength.
Unfortunately, emissivity of the components may vary over time due to changes in temperature, buildup of residue on the components and/or oxidation of turbine components. In addition, emissivity measurements may be affected by dirt accumulation on the viewing port window. Furthermore, turbine components which include a thermal barrier coating (TBC) may be subject to spall, a condition in which portions of the TBC detach from the surface of the component, thereby exposing the base material. As will be appreciated, the emissivity of the base material may be significantly higher than the emissivity of the TBC. Consequently, pyrometry systems which assume a constant emissivity may provide inaccurate temperature measurements for spalling turbine components. For example, a pyrometry system configured to measure radiation within a fixed wavelength range may detect an increased radiant intensity from a turbine component having a spalled region. Because the pyrometry system is unable to distinguish between increased temperatures and increased emissivity, the pyrometry system will report a higher temperature. Consequently, an operator or an automatic system may deactivate the turbine engine to determine the cause of the increased turbine component temperature. Because the actual temperature of the turbine component may be within a desired operating range, such an operation may unnecessarily reduce the availability of the turbine engine.